The invention relates to a double pump including a main pump and a secondary pump which are driven by way of a common shaft, and in particular to a rotary vane pump as the main pump and a radial piston pump as the secondary pump. Still more specifically, the invention relates to the shaft of the double pump having a cam for driving the secondary pump.
A double pump of that kind is known from U.S. Pat. No. 2,605,707 to R. F. Worlidge, the cam being keyed on the shaft and supporting on its outer surface a needle roller bearing journalling a rotary ring which drives the pistons of a radial piston pump. If one of these pistons is jamming, the radial piston pump fails as a whole, and it may happen that the drive shaft is locked so that the further rotary pump also fails. Such double failure can be disastrous in vehicle applications.